Embryo cryopreservation

Introduction

The maintenance of mouse colonies can be expensive and time consuming. Embryo cryopreservation offers the researcher an alternative to maintenance breeding to preserve a mouse line that is not in current use. Embryo cryopreservation also provides a back-up to preserve the line in the unlikely event that the colony becomes pathogen compromised, has a fertility issue or background/genotype is compromised.

When deciding to cryopreserve a line, the client will need to choose if embryo or sperm freezing is best suited to the strain.

Table showing the pros and cons of freezing embryos vs freezing sperm.

Embryos will be stored in 2 separate cryopreservation vessels/sites.

The number of embryos stored is determined by the mating strategy used to produce the embryos for freezing.

Homozygous X Homozygous = 250 embryos- all re-derived progeny will be homozygous.
Homozygous X Het or Wild type = 250 embryos- re-derived progeny will have varying genotype, therefore will need to be screened for genotype.
Heterozygous X Heterozygous = 300 embryos- re-derived progeny will have varying genotype, therefore will need to be screened for genotype
Heterozygous X Wild type = 500 embryos- re-derived progeny will have varying genotype, therefore will need to be screened for genotype

All strains cryopreserved at TASQ remain the property of the Client and will not be distributed without the permission of the Client.

Embryo production

Mice needs

The number of females required per strain to produce the predetermined number of embryos will vary between strains. There are many factors affecting the success of embryo production, including the age of the females, the strain background and fertility of the males. Therefore it is not possible to accurately predict the exact number of embryos that will be produced per female.

Females are preferred at between 3 and 16 weeks of age. At this age the females are more receptive to the super-ovulation regime, thereby producing more viable eggs. This will reduce the overall number of females required. A minimum of 20 females will be required.

If the required number of embryos has not been reached after the initial 20 females are used, TASQ will discuss with the Client the number of additional females that may be needed to reach the required number of embryos.

Wild type females can be purchased on the Client’s behalf.

Males with proven fertility are preferred but not essential. A minimum of 3 males will be required. Stud males should be aged between 2 and 6 months for best results. Ex-breeders can also be used.

If these numbers are not available a different strategy may be required. Please contact TASQ for consultation.

Embryos are frozen by rapid cooling of the 4-8 cell embryo.

Costs

Additional costs

How to start

Contact TASQ.
Health reports from the animal facility where the donor mice reside will need to be sent to TASQ (if applicable).
Complete online registration form Request to Cryopreserve
Once health reports have been reviewed, TASQ will liaise with your Animal Facility Manager to have the mice shipped to the necessary UQ animal facility.
Embryo freezing will be scheduled, with TASQ notifying the Client of the starting date.

Additional notes

TASQ will freeze all viable embryos collected.
TASQ will schedule IVF runs until all females supplied have been used. TASQ will notify the Client of the viable embryo numbers frozen and await instructions depending on the number of embryos obtained. If more females are required to reach the embryo numbers needed TASQ will request a further shipment of females.
TASQ will perform a test thaw of one straw. This will involve the thawing and culturing of the embryos to assess viability. Cultured embryos will then be transferred to a pseudopregnant female to assess the viability of live birth. TASQ can not guarantee that 100% of embryo transfers will result in live births. TASQ will notify the Client of the success of the test thaw. TASQ cannot guarantee all mouse strains’ embryos will tolerate and survive the freeze/thaw procedure.
Once the embryo numbers have been reached, the Client will be notified of the completion of freezing. At this time the Client will be asked if the donor and stud stocks held at the UQ animal facility can be euthanised. TASQ must have this confirmation in writing. Stocks must not be euthanised at the Client’s facility until discussion with TASQ regarding further needs for the embryo freezing program have taken place.
A TASQ registration form - must be completed prior to service commencement.
A current AEC certificate and OGTR number must be supplied prior to commencement of service.
Download the “UQBR Cryopreservation and Rederivation Services Information and Protocol Booklet”which has additional information for Clients.